Non-Patent Literature 1 defines a specification of a switch (OpenFlow Switch; below, “OFS”) in a network known as OpenFlow. In OpenFlow, a control apparatus known as an OpenFlow controller (below, “OFC”) is disposed. A flow table held by an OFS contains entries (flow entries) that associate a match condition (Match Fields) which matches received packets, and processing content (Instructions) to be applied to packet(s) matching the match condition. The OFC can perform detailed control of flow units by operating on content (adding a new entry, modifying, deleting, and the like) of a flow table held by an OFS under its control.
A match condition (Match Fields) redefines, as one unit, a data range of layer 1-layer 4 in an OSI reference model defined in Ethernet (registered trademark) and TCP/IP. Specifically, a broad range of information can be set as match condition(s) (Match Fields), such as a port of a physical switch, an IEEE 802.1Q specified VLAN ID, a MAC (Media Access Control) address, an IP (Internet Protocol) address, a TCP (Transmission Control Protocol) port number, or the like, and fine grained modification of packet processing is possible.
As processing content (Instructions), a relevant packet may be forwarded to another port, or may be dropped without forwarding, for example. In OpenFlow Switch Specification Version 1.1.0 of Non-Patent Literature 1, as processing content (Instructions), it is possible to implement pipeline processing executing content of a plurality of processes using a plurality of flow tables, by setting a command (Go-to Table) instructing a transition to another flow table (refer to Non-Patent Literature 1, “4.1.1 Pipeline Processing”).
Patent Literature 1 discloses a controller equivalent to the abovementioned OFC, which performs load balancing of a service-providing server by modifying flow entries set in switches in response to a request for load balancing from the service-providing server that provides a service to a client terminal.
Patent Literature 2 discloses a managing computer by which it is possible to curtail entry overflow in a plurality of switches disposed in a communication network. In the publication, there is a description that a managing computer refers to parameters (entry state information) depending on the number of used entries of respective switches, to calculate end-to-end switch cost, and to determine a path with minimum switch cost as a flow path.